A known transmission shift device for a vehicle is provided to change a shift stage. Such a shift device includes a holding mechanism holding a sleeve of a shift device in a neutral state and in each of the shift states of the shift stage. For example, as disclosed in JPH9-177823A (hereinafter referred to as Patent reference 1), a shift device shifts a sleeve meshed with a synchronizer hub fixed at a rotary shaft in an axial direction of the rotary shaft using, for example, a motor when changing a shift stage. At this time, by shifting the sleeve in the axial direction, the synchronizer ring is pressed by a leaf spring positioned between the sleeve and the synchronizer ring, and accordingly, presses against a clutch gear. Thus, respective rotary speeds of the sleeve, synchronizer ring and the clutch gear are gradually synchronized with one another. Then, an inner circumference of the sleeve is meshed with an outer circumference of the clutch gear to establish a desired shift state.
The leaf spring, as a holding mechanism holding the sleeve, includes one projection facing the sleeve and two projections facing the synchronizer ring. When the projection facing the sleeve engages with a center recessed portion of the sleeve, the center recessed portion of three recessed portions formed side-by-side in the axial direction at the inner circumferential surface of the sleeve, the sleeve is held in the neutral state. When the projection facing the sleeve engages with one of the recessed portions positioned at opposing ends in the axial direction of the three recessed portions, the sleeve is held in either of the shift states. Two projections projecting toward the synchronizer ring engage with respective recessed portions formed at the synchronizer ring. Thus, when the sleeve is held in the neutral state, the synchronizer ring is held to be close to the sleeve.
According to Patent reference 1, the leaf spring is fixed by engaging with cutouts of the synchronizer ring facing against the leaf spring. Thus, for example, the construction disclosed in Patent reference 1 cannot be applied to a shift device which includes a dog clutch without the synchronizer ring. Further, because the three recessed portions are formed side-by-side in the axial direction at the inner circumferential surface of the sleeve, the size of the shift device may be increased due to the long axial length. While the sleeve requires a strong holding force in the neutral state to increase the reliability, the holding force cannot be increased because the change of the position of the recessed portions engaged with the projections is the only operation to be done by the shift device when the shift device is shifted between the neutral state and the shift states.
A need thus exists for a transmission shift device which is not susceptible to the drawback mentioned above.